This invention relates to a method of treating a silicon nitride film formed by plasma deposition (hereinafter called "plasma silicon nitride film"), to prevent cracking of the silicon nitride film which is used for manufacturing semiconductor devices.
One conventional method for preventing the formation of cracks in a plasma silicon nitride film is a method dependent upon controlling the various parameters involved in forming the film such as pressure, amount of gas flow, and concentration ratio between monosilane and ammonia gas, (M. J. Rand; J. Vac. Sci. Technol., Vol. 16, 1979, p. 420). According to this method, conditions are selected in which inner stress which causes cracks is minimized by optimization of the various parameters involved in forming the film. After the film is formed, no special treatment for preventing cracks is employed.
In the conventional method described above, it is necessary to control many parameters, and it is very difficult to maintain the optimum conditions because the film forming equipment usually has different characteristics from one piece of equipment to the next.
Further, effective high temperature heat treatment (annealing) to reduce inner stress cannot be applied to the film because most semiconductor devices have aluminum connection layers which are covered by the plasma silicon nitride film and which would melt during the high temperature heat treatment.